Ore flotation collector and ore flotation process



United States Patent 3,114,704 ORE FLOTATION COLLECTGR AND ORE FLOTATION PROCEdS Robert S. Kauiiman, Palos Heights, Robert E. Baarson, Chicago, and Harold B. Treweeli, Park Forest, 111., assignors to Armour and Company, Chicago, 111., a corporation of Delaware No Drawing. Filed Apr. 20, 1961, Ser. No. 104,242 6 Claims. ((31. 209-166) This invention relates to an ore flotation collector which has particular utility in the froth flotation of silica containing phosphate ores, and therefore the invention also relates to a phosphate ore flotation process.

At the present time primary fatty monoamines are widely used in the froth flotation of silica containing phosphate ores. The amine flotation is commonly employed for the final concentration of the phosphate rock, the coarse silica having been separated in an earlier flotation stage. The amines are ordinarily used in their salt form, such as the acetate salt. The amine collector, being strongly cationic, causes the silica to float and it is removed in the froth or overflow. The desired product, being the concentrated phosphate rock, is removed in the underflow. The phosphate concentrate thus produced should contain a minimum of silica, preferably not more than 3 or 4% by weight.

Since amine collectors have become virtually standard reagents in the flotation of phosphate ores, a great deal of research has been directed toward the improvement of such collectors. In evaluating amine collectors two factors are of major importance. These are the strength of the collector, which is a measure of the quantity of the collector required to obtain a particular degree of separation, and the selectivity of the collector, which is a measure of the amount of the phosphate rock recovered. For example, collector strengths can be evaluated in terms of the pounds of collector required per ton of flotation feed to obtain a particular concentration of acid insolubles (a measure of silica content) in the product. Collector selectivity can be determined by comparing the percent of phosphate rock recovered with the percent of insolubles in the product. The recovery may be stated in terms of tricalcium phosphate content which is usually designated in the industry as bone phosphate of lime (BlL). As indicated, the siliceous gangue constituents of the phosphate rock are commonly determined and reported as acid insolubles (Insol).

One disadvantage of the amine collectors used for phosphate ore recovery is the relatively high cost of the collectors. In addition to the desire to increase the strength of amine collectors and/ or their selectivity, there has been a desire to find means for reducing the cost of such collectors. The way in which these and other objects are achieved will be indicated in the following detailed specification.

For many years fatty nitriles have been prepared commercially on a large scale by the reaction of naturally occurring fatty acids with ammonia. The details of such processes vary, but the basic reactions are the same. For example, the nitriles may be prepared as described in U.S. Patent No. 2,314,894, or as described in U.S. Patent No. 2,808,426. In all such processes a relatively non-volatile residue is obtained, which is known as nitrile pitch. At the present time millions of pounds per year of such nitrile pitch are produced as a by-product of fatty nitrile manufacturers. Heretofore the nitrile pitch has had little commercial value, and is commonly used as a fuel by the nitrile manufacturers. It will be evident therefore that the current market price of nitrile pitch is much less than that of the primary fatty monoamines which are used as ore flotation reagents.

This invention is based in part on the discovery that by hydrogenating the nitrile pitch and combining the hydrogenated pitch in certain proportions with primary fatty monomaines that an ore flotation collector can be produced which is of equal or greater effectiveness to the straight primary amines. Since the hydrogenated nitrile pitch may comprise as much as 40 to 60% of the collector, the cost of the collector is greatly reduced. Furthermore, when the preferred proportions are employed, the collector will not only be of substantially lower cost, but it will also have improved selectivity and/ or collector strength.

The nitrile pitch as produced, for example, by the procedures described in US. Patent Nos. 2,314,894 and 2,808,426, will contain nitriles as the principal component and will be composed of compounds and polymers therefrom containing in excess of 22 carbon atoms. Most natural fats are composed predominantly of fatty acids containing from 12 to 22 carbon atoms (C to C and when these are reacted with ammonia to produce the corresponding nitrile monomers the residue or pitch will contain a high percentage of high boiling compounds of a polymeric nature. These may include nitriles, amides, fatty acids, esters, etc. The exact chemical composition of all of the compounds present in nitrile pitch is virtually impossible to determine by standard analytical procedures. However, a typical polymeric nitrile pitch may contain from 25 to 60% nitrile, 5 to 30% amide, l to 10% fatty acid, 1 to 15% ester, and a variable percentage of other high boiling compounds, the percentages being on a weight basis. As indicated previously, most of the compounds in the pitch will be of a polymeric nature, although the pitch may also contain small percentages of some monomeric compound including monomeric nitriles.

In accordance with the present invention, the nitrile pitch is subjected to hydrogenation to convert a major pot-tion of the nitriles in the pitch to their corresponding amines. The hydrogenated pitch will therefore also be a relatively high boiling material composed of compounds of normal carbon chain length and compounds and polymers therefrom having more than 22 carbon atoms. This is true even when the original fatty acids contain from 12 to 18 carbon atoms, as preferred, because of the availability of natural fats containing such fatty acids. For example, the fatty acid source may be tallow, coconut oil, soybean oil, cottonseed oil, or mixtures thereof.

The hydrogenation can be carried out in accordance with standard procedures for hydrogenating fatty nitriles to produce the corresponding amines. Raney nickel may be used as a catalyst, the hydrogenation being carried out at an elevated temperature and pressure. For example, temperatures of to 170 C. may be used, and pressures of 100 to 300 psi. Higher pressures and catalyst ratios may be used but to no particular advantage. For example, a reactor temperature of C. and a pressure of 200 p.s.i. may be advantageously used.

While it is not necessary to convert 100% of the nitriles in the pitch to the amine, it will usually be desirable to continue the hydrogenation reaction for a sufficient time to convert at least the major portion of the nitriles. This may normally be accomplished Without excessive hydrogenation times. For example, the hydrogenation reaction may be carried out in from 2. to 6- hours. It will be understood that the reaction time will depend some-what on the temperatures and pressures employed as well. as the proportion of catalyst. The proportion of catalyst, however, can be varied considerably. Suitable proportions of Raney nickel range from 0.1 to 1 percent based on the nitrile pitch. A proportion of 0.6% of the catalyst gives good results.

The hydrogenated nitrile pitch is then combined with the primary fatty monoamine. These two components should be thoroughly mixed and blended to produce a uniform product. The resulting ore flotation collector should contain at least of the hydrogenated nitrile pitch on a weight basis but not over 60%. With such formulations, the ore flotation collector would correspondingly contain from 40 to 95% by weight of the primary fatty monoamine. It will be understood that the primary fatty monoamine is the type which has heretofore been used as an ore flotation collector, that is, the primary amine will usually be composed essentially of amines containing from 12 to 22 carbon atoms, and preferably from 16 to 22 carbon atoms. For achieving the maximum benefits of the present invention, it is preferred that the ore flotation collector contain at least 40% but not over 75% by weight of the primary amine, the corresponding percentages of the nitrile pitch being from 25 to 60%.

The ore flotation collector prepared as described in the foregoing specification can be used in the separation of silica from phosphate rock in the same manner as the primary fatty monoamines would be employed. In other words, all that is necessary is to subject the silica-containing phosphate ore to froth flotation in the presence of the improved collector. No new or special operating techniques are required. Since the details of froth flotation as applied to the treatment of phosphate ores are wellknown, it is thought to be unnecessary to repeat them here. In accordance with known procedures, the flotation feed will be deslimed, conditioned with the collector for a brief but finite time at or near flotation pulp density, and subject it to froth flotation in the flotation cell. In the operation of the cell, the silica or tails will be removed with the froth or overhead, and the concentrated phosphate rock will be recovered in the underflow. It will be understood that the collector in addition to the components previously described may contain a minor proportion of secondary or tertiary amines. Commercial grades of primary amines may contain from 5 to of secondary amines together with smaller percentages of tertiary amines.

It will also be understood that the amines in the collector may be employed in their salt form, that is, as the acetates, hydrochlorides, etc. In other words, the amine groups of the various amine compounds in the collector may be reacted with acetic acid or other acidic reagent to form amine salts before the collector is used in the flotation cell.

The present invention is further illustrated by the fol lowing examples.

Example 1 360 parts of nitrile pitch was subjected to hydrogenation. The pitch was obtained in the manufacture of nitriles from tallow fatty acids by reacting the fatty acids with ammonia and the recovery of the nitrile product by distillation. 367 parts of the nitrile pitch was introduced into an autoclave together with 7.3 parts of Raney nickel and 3 drops of 50% caustic (aqueous NaOH) for each 7.3 grams of Raney nickel. The flow of hydrogen was started and the reaction was carried out at 130 C. and 150 p.s.i. for 3 hours. The pressure was then increased to 200 p.s.i. and held for 1 hour, after which the reaction mixture was cooled.

The analysis of the nitrile pitch before hydrogenation was: nitrile 50%, amide 12.4%, fatty acid 4.8%, ester 8.6%, unidentified 24.2%. An analysis of the hydrogenated pitch indicated that it contained 49.6% of amine, indicating that the conversion of the nitrile was substantially complete.

Example 2 A hydrogenated nitrile pitch is prepared as previously described in Example 1. The starting material was derived from a mixture of fatty acid sources containing mainly 16 to 18 carbon atoms. After hydrogenation it contained 31.2% total primary amine (analyzed as tallow amine) and had a combining weight of 840. This hydrogenated material is in turn combined with primary tallow amine in several different proportions to provide cationic flotation collectors differing with respect to total primary amine content and combining weight, as summarized below.

Percent Percent Hydrogen- Primary Reagent N o. ated Amine Nitrile (Analyzed Pitch as Tallow) Tests were conducted with the above collectors on samples of deslimed cationic-circuit phosphate feed received from a Florida phosphate operation. The flotation feed contained 16% acid insoluble and 66.6% BPL (30.5% P 0 For each flotaiton test, a 500 g. ore sample was conditioned at flotation pulp density (16% solids) in a Fagergren flotation cell for /4 min. with amine primary collector, kerosene (in a constant 2:1 ratio by weight with the amine), and 0.10 lb./ton of Dowfroth 250. Following conditioning, air was admitted to the cell and a silica froth product was collected.

The results were as follows:

Lb. Percent Reagent N o. Reagent/ Percent Percent BLP re- Ton of HPL Insol. covery Feed The improved phosphate (BPL) recovery for flotation with reagents Nos. 1-3 as compared to reagent No. 4, a high purity technical grade tallow amine, illustrates the particular utility of the invention.

In the foregoing specification, the use of the ore flotation collector has been illustrated primarily in connection with phosphate ore recovery. It will be understood, however, that the collector may be used as a cationic flotation reagent for other purposes, such as the recovery of feldspar and minerals of the mica group like muscovite, biotite, and vermiculite.

In the foregoing specification this invention has been described in connection with certain specific embodiments thereof and many details have been set forth for purpose of illustration. However, it will be apparent to those skilled in the ore flotation art that the invention is susceptible to additional embodiments and that many of the details described herein can be varied considerably without departing from the basic principles of the invention.

We claim:

1. An ore flotation collector, comprising from 5 to by weight of hydrogenated nitrile pitch in admixture with from 40 to 95% of a primary fatty monoamine, said pitch having been prepared by hydrogenating the relatively nonvolatile residues obtained in the manufacture of nitriles wherein C to C fatty acids are reacted with ammonia and the nitrile product is recovered by distillation, said hydrogenation having converted the major proportion of the nitriles in said pitch to amines and said hydrogenated nitrile pitch being composed predominately of compounds containing in excess of 22 carbon atoms, and said primary amine being composed essentially of amines containing from 12 to 22 carbon atoms.

2. The ore flotation collector of claim 1 where said collector contains from 25 to 60% by weight of said hydrogenated nitrile pitch and from 40 to of said primary amine.

3. A phosphate ore flotation process characterized by subjecting silica-containing phosphate ore to froth flota tion in the presence of the collector of claim 1.

4. The process of claim 3 wherein said collector contains from to 60% of said hydrogenated nitrile pitch and from to 75% by weight of said primary amine.

5. An ore flotation collector, comprising from 25 to by weight of hydrogenated nitrile pitch in admixture with from 40 to of a primary fatty monoamine, said pitch having been prepared by hydrogenating the relatively non-volatile residues obtained in the manufacture of nitriles wherein C to C fatty acids are reacted with ammonia and the nitrile product is recovered by distillation, said residues containing nitriles as the principal component and being composed predominately of compounds containing in excess of 22 carbon atoms, said hydrogenation having converted a major portion of said nitriles to amines, said primary fatty monoamine being com osed essentially of amines containing from 16 to 22 carbon atoms.

6. A phosphate ore flotation process characterized by subjecting silica-containing phosphate ore to froth flotation in the presence of the collector of claim 5.

References Cited in the file of this patent UNITED STATES PATENTS 2,122,644 Harwood Oct. 8, 1936 2,166,150 Howk July 18, 1939 2,298,281 Corley et al Oct. 13, 1942 2,576,464 Longmeier Aug. 5, 1949 2,818,976 Lentz Ian. 7, 1958 2,857,331 Hollingsworth Oct. 21, 1958 2,914,174 Haseman Nov, 24, 1959 FOREIGN PATENTS 524,261 Italy Apr. 21, 1955 

1. AN ORE FLOTATION COLLECTOR, COMPRISING FROM 5 TO 60% BY WEIGHT OF HYDROGENATED NITRILE PITCH IN ADMIXTURE WITH FROM 40 TO 95% OF A PRIMARY FATTY MONOAMINE, SAID PITCH HAVING BEEN PREPARED BY HYDROGENATING THE RELATIVELY NONVOLATILE RESIDUES OBTAINED IN THE MANUFACTURE OF NITRILES WHEREIN C12 TO C22 FATTY ACIDS ARE REACTED WITH AMMONIA AND THE NITRILE PRODUCT IS RECOVERED BY DISTILLATION, SID HYDROGENATION HAVING CONVERTED THE MAJOR PROPORTION OF THE NITRILES IN SAID PITCH TO AMINES AND SAID HYDROGENATED NITRILE PITCH BEING COMPOSED PREDOMINANTLY OF COMPOUNDS CONTAINING IN EXCESS OF 22 CARBON ATOMS, AND SAID PRIMARY AMINE BEING COMPOSED ESSENTIALLY OF AMINES CONTAINING FROM 12 TO 22 CARBON ATOMS. 